package edu.object_oriented.demo;

public class Test {

    public static void main(String[] args) {
        Student stu = new Student();
        stu.name = "jack";
        //......
        Phone phone = new Phone();
        phone.memory = 12;
        //....... NullPointerException  空指针异常
        Phone phone2 = null;
        phone2.memory = 8;

    }

}
